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Chapter 15
The Urinary System
Functions of the Urinary System
1. Elimination of waste
 Nitrogenous wastes
 Toxins
 Drugs
2. Regulates homeostasis
 Water balance
 Electrolytes
 Acid-base balance in the blood
 Blood pressure
 RBC blood cell production
 Activation of vit. D
Importance of Water in Human Body
• Water helps to remove the dangerous toxins
that our body takes in from the air, the food
and the chemicals we use on our skin and hair.
• Water also provides cushion for our body
joints.
• Water carries oxygen and nutrients into all our
cells.
• Water also helps to regulate our body
temperature.
Our body has integrative body
systems.
When we say “integrative”, this means that our
body systems are interconnected to each
other to maintain homeostasis.
What is human homeostasis?
Word origin: from the
Greek: homeo, meaning unchanging
+ stasis, meaning standing.
• Human homeostasis refers to the body's
ability to physiologically regulate its inner
environment to ensure its stability, in
response to fluctuations in the outside
environment.
• it is the state of balance in our body.
What will happen if you do not have
the ability to maintain homeostasis in
our body?
Homeostatic imbalance will lead to diseases or
even death.
Maintaining
Chemical
Homeostasis
The Urinary
System
Organs of the Urinary system
 Kidneys
 Ureters
 Urinary bladder
 Urethra
Location of the Kidneys
 Right lower than left
 Attached to ureters, renal
blood vessels, & nerves at
renal hilus
 Atop kidney is adrenal
gland
Regions of the Kidney
 Renal cortex –
outer region
 Renal medulla –
inside the cortex
 Renal pelvis –
inner collecting
tube
Blood Flow in the Kidneys
Nephrons
 Structural and
functional units of
the kidneys
 Forms urine
 Main structures
a. Glomerulus
b. Renal tubule
nephron
renal artery
renal vein
Kidney
Anatomy
Nephrons
 Excess salts, water, wastes
remain in the tubule and
become urine
 Urine enters collecting ducts
(tubes) in the medulla
 Collecting tubes empty into
the renal pelvis (first section
of the ureter)
 All the blood in the body
passes through the kidneys
about 20 times every hour.
Glomerulus
 Actual Filtration occurs here
 Excess salts, water,
nitrogenous wastes
 Water and solutes smaller
than proteins are forced
through capillary walls
 Blood cells too big to filter
 Becomes urine
Renal Tubule
 Collecting tube
 Reabsorption


Things that are useful to the
body are brought back into
circulation.

water, glucose, amino acids,
and sodium.
NOT: Nitrogenous waste products
- Urea
- Uric acid
-Creatinine
-Excess water
Characteristics of Urine
 Yellow due to
pigment urochrome
(from break-down of
hemoglobin) &
solutes
 Sterile
 Slightly aromatic
 Normal pH of ~ 6
 Specific gravity of
1.001 to 1.035
Ureters
The urine leaves
the kidneys
through the
ureters, a
muscular tubes 25
to 30 cm long that
moves urine from
the kidney to the
urinary bladder.
Urinary Bladder
 Smooth, collapsible,
muscular sac
 Temporarily stores urine
 Trigone – 3 openings
- Two from ureters
- One to urethrea
Urethra
 Thin-walled tube
 Carries urine from bladder by peristalsis
 Release controlled by 2 sphincters
- Internal urethral sphincter (involuntary)
- External urethral sphincter (voluntary)
Urethra Gender Differences
 Length
- Females – 3–4 cm (1
inch)
- Males – 20 cm
inches)
(8
 Location
- Females – along wall of
the vagina
- Males – through the
prostate and penis
 Function
- Females – only urine
- Males –urine and sperm
Micturition (Voiding)
Both sphincters
must open
-
internal relaxes after bladder
stretches
-
Activation - impulse to spinal cord
and back via pelvic splanchnic
nerves
-
external voluntarily relaxes